1. Field of the Invention
This invention relates to a method and apparatus for measuring the output torque of automotive engine. Specifically, a sensing system includes components mounted to a driveshaft that are used to measure the twist of the driveshaft under load to determine engine torque.
2. Related Art
Engine torque is a critical parameter that allows a vehicle to accelerate. For heavy duty vehicles, there are acceleration and overall torque output requirements that need to be met in order to satisfactorily perform designated duty cycles. As more auxiliary loads are run off of vehicle engines, torque losses frequently occur causing poor engine performance. These auxiliary loads such as air conditioning, alternators, generators, power steering, or power take-offs consume a portion of the engine torque that would normally satisfy the acceleration and output torque requirements. Thus, it is very important to be able to accurately measure engine torque.
There are different types of engines such as gas and diesel engines, for example. Engines typically have a number of cylinders that are driven by a common crankshaft. In a gas powered internal combustion engine, the cylinders each have a piston, a spark plug, and a connecting rod that interconnects the piston and the crankshaft. A fuel system supplies fuel to each of the cylinders, which is ignited by the spark plug to generate power or output torque. Typically a processor or other similar apparatus is used to control the fuel supply to the engine. If the torque for each cylinder could be measured, a closed torque control system could be utilized to provide independence from auxiliary loads. A closed system that separately identifies each cylinder torque can ease tolerances on fuel injection components because adjustments are easily made in the fuel control system.
Several different methods have been used to measure engine torque, however, there is no simple method for determining an individual torque for each engine cylinder. One method for measuring engine torque has a sensor mounted on the engine to generate a signal with different amplitudes for each engine cylinder. This results in a complex signal that is difficult to translate. Another method determined torque by using engine speed changes. Another method has a sensor mounted in the engine that utilizes Hooke's law to determine an engine output torque but the output is not used to determine torque for each cylinder.
It is the object of the present invention to provide a simple and effective apparatus and method for calculating engine torque on a cylinder by cylinder basis that overcomes the deficiencies outlined above. Further, this method will allow the fuel system to be easily adjusted to compensate for auxiliary loads.